Device to Device (D2D) communication is being studied in communication standard groups to enable data communication services between User Equipment's (UEs). During the D2D communication a transmitting D2D UE (i.e., source UE) can transmit data packets to a group of D2D UEs (i.e., destination UE) or broadcast data packets to all the D2D UEs. The D2D communication between a transmitter and receiver(s) is connectionless in nature (i.e. there is no connection setup (or no control messages are exchanged) between the transmitter and a receiver) before the transmitter starts transmitting the data packets. During the transmission, the transmitter includes source identification (ID) and destination ID in the data packets. The source ID is set to the UE ID of the transmitter. The destination ID is the intended recipient of the transmitted packet. The destination ID indicates whether the packet is a broadcast packet or a packet intended for a group. The destination ID for broadcast is an ID reserved from group IDs. The UE is assigned a D2D UE ID for its associated group.
A D2D Media Access Control (MAC) Protocol Data Unit (PDU) for carrying one or more MAC Service Data Units (SDUs) for the D2D communication includes a MAC header and a MAC payload. The payload comprises of one or more MAC SDUs corresponding to same destination i.e. group or broadcast. The source (SRC) field in the MAC header is set to D2D UE identifier (ID) of the source. The D2D UE ID is unique within the group i.e. each member of the group has distinct D2D UE ID. The destination (DST) field in the MAC header is set to 16 most significant bits (MSBs) of 24 bit D2D Layer-2 group ID of the destination group. The 8 least significant bits (LSBs) of 24 bit D2D Layer-2 group ID is transmitted in Scheduling Assignment (SA) or Scheduling Control (SC) information. The SA or SC information is transmitted prior to transmission of D2D MAC PDU. The current D2D MAC PDU format does not support a unicast D2D communication i.e., D2D MAC PDU cannot be addressed to a destination UE.